import sys
from json import loads

from galaxy.datatypes.tabular import Tabular


class BaseDataProvider(object):
    """
    Base class for data providers. Data providers (a) read and package data from datasets;
    and (b) write subsets of data to new datasets.
    """

    def __init__(self, converted_dataset=None, original_dataset=None, dependencies=None,
                 error_max_vals="Only the first %i values are returned."):
        """ Create basic data provider. """
        self.converted_dataset = converted_dataset
        self.original_dataset = original_dataset
        self.dependencies = dependencies
        self.error_max_vals = error_max_vals

    def has_data(self, **kwargs):
        """
        Returns true if dataset has data in the specified genome window, false
        otherwise.
        """
        raise Exception("Unimplemented Function")

    def get_iterator(self, **kwargs):
        """
        Returns an iterator that provides data in the region chrom:start-end
        """
        raise Exception("Unimplemented Function")

    def process_data(self, iterator, start_val=0, max_vals=None, **kwargs):
        """
        Process data from an iterator to a format that can be provided to client.
        """
        raise Exception("Unimplemented Function")

    def get_data(self, chrom, start, end, start_val=0, max_vals=sys.maxsize, **kwargs):
        """
        Returns data as specified by kwargs. start_val is the first element to
        return and max_vals indicates the number of values to return.

        Return value must be a dictionary with the following attributes:
            dataset_type, data
        """
        iterator = self.get_iterator(chrom, start, end)
        return self.process_data(iterator, start_val, max_vals, **kwargs)

    def write_data_to_file(self, filename, **kwargs):
        """
        Write data in region defined by chrom, start, and end to a file.
        """
        raise Exception("Unimplemented Function")


class ColumnDataProvider(BaseDataProvider):
    """ Data provider for columnar data """
    MAX_LINES_RETURNED = 30000

    def __init__(self, original_dataset, max_lines_returned=MAX_LINES_RETURNED):
        # Compatibility check.
        if not isinstance(original_dataset.datatype, Tabular):
            raise Exception("Data provider can only be used with tabular data")

        # Attribute init.
        self.original_dataset = original_dataset
        # allow throttling
        self.max_lines_returned = max_lines_returned

    def get_data(self, columns=None, start_val=0, max_vals=None, skip_comments=True, **kwargs):
        """
        Returns data from specified columns in dataset. Format is list of lists
        where each list is a line of data.
        """
        if not columns:
            raise TypeError('parameter required: columns')

        # TODO: validate kwargs
        try:
            max_vals = int(max_vals)
            max_vals = min([max_vals, self.max_lines_returned])
        except (ValueError, TypeError):
            max_vals = self.max_lines_returned

        try:
            start_val = int(start_val)
            start_val = max([start_val, 0])
        except (ValueError, TypeError):
            start_val = 0

        # skip comment lines (if any/avail)
        # pre: should have original_dataset and
        if(skip_comments and
                self.original_dataset.metadata.comment_lines and
                start_val < self.original_dataset.metadata.comment_lines):
            start_val = int(self.original_dataset.metadata.comment_lines)

        # columns is an array of ints for now (should handle column names later)
        columns = loads(columns)
        for column in columns:
            assert((column < self.original_dataset.metadata.columns) and
                   (column >= 0)), (
                "column index (%d) must be positive and less" % (column) +
                " than the number of columns: %d" % (self.original_dataset.metadata.columns))

        # set up the response, column lists
        response = {}
        response['data'] = data = [[] for column in columns]
        response['meta'] = meta = [{
            'min'   : None,
            'max'   : None,
            'count' : 0,
            'sum'   : 0
        } for column in columns]

        column_types = [self.original_dataset.metadata.column_types[column] for column in columns]

        # function for casting by column_types
        def cast_val(val, type):
            """ Cast value based on type. Return None if can't be cast """
            if type == 'int':
                try:
                    val = int(val)
                except ValueError:
                    return None
            elif type == 'float':
                try:
                    val = float(val)
                except ValueError:
                    return None
            return val

        returning_data = False
        f = open(self.original_dataset.file_name)
        # TODO: add f.seek if given fptr in kwargs
        for count, line in enumerate(f):

            # check line v. desired start, end
            if count < start_val:
                continue
            if (count - start_val) >= max_vals:
                break

            returning_data = True

            fields = line.split()
            fields_len = len(fields)
            # NOTE: this will return None/null for abberrant column values (including bad indeces)
            for index, column in enumerate(columns):
                column_val = None
                column_type = column_types[index]
                if column < fields_len:
                    column_val = cast_val(fields[column], column_type)
                    if column_val is not None:

                        # if numeric, maintain min, max, sum
                        if(column_type == 'float' or column_type == 'int'):
                            if((meta[index]['min'] is None) or (column_val < meta[index]['min'])):
                                meta[index]['min'] = column_val

                            if((meta[index]['max'] is None) or (column_val > meta[index]['max'])):
                                meta[index]['max'] = column_val

                            meta[index]['sum'] += column_val

                # maintain a count - for other stats
                meta[index]['count'] += 1
                data[index].append(column_val)

        response['endpoint'] = dict(last_line=(count - 1), file_ptr=f.tell())
        f.close()

        if not returning_data:
            return None

        for index, meta in enumerate(response['meta']):
            column_type = column_types[index]
            count = meta['count']

            if((column_type == 'float' or column_type == 'int') and count):
                meta['mean'] = float(meta['sum']) / count

                sorted_data = sorted(response['data'][index])
                middle_index = (count / 2) - 1
                if count % 2 == 0:
                    meta['median'] = ((sorted_data[middle_index] + sorted_data[(middle_index + 1)]) / 2.0)

                else:
                    meta['median'] = sorted_data[middle_index]

        # ugh ... metadata_data_lines is not a reliable source; hafta have an EOF
        return response
